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Measuring change using communication rating scales: the case for Rasch analysis, as illustrated with the ASHA FACS.

Article Excerpt
More than a decade ago, the authors of the American Speech-Language-Hearing Association Functional Assessment of Communication Skills for Adults (ASHA FACS; Frattali, Thompson, Holland, Wohl, & Ferketic, 1995) purported that the instrument would "enhance ... documentation of progress" and "yield a robust body of functional outcome data" (manual, p. 7). However, because of its ordinal rating scale format, valid mathematical calculations of improvement on the ASHA FACS cannot be performed (Merbitz, Morris, & Grip, 1989). Moreover, the relative difficulty of ASHA FACS items has never been determined. Therefore, meaningful progress along a continuum from simple to more challenging functional communication tasks cannot be identified. In this column, we discuss the need for Rasch analysis (Rasch, 1980) to convert such ordinal, communication rating scales to equal-interval measures appropriate for evaluating and interpreting patient progress.

The ASHA Functional Communication Measures Project Advisory Group (ASHA, 1990) specified that functional assessment of communication should assess "the extent of ability to communicate with others in a variety of contexts" (p. 2). The ASHA FACS is the most frequently used assessment of functional communication in adults with aphasia (Ross, 2007). The scale is conceptually grounded in the World Health Organization's (1980) model of international classification of impairments, disabilities, and handicaps (ICIDH). In this framework, difficulty with functional communication may be conceptualized at the disability level as a functional consequence of language impairment. Accordingly, the ASHA FACS permits a clinician or significant other to rate the functional consequences of language impairments on an individual's basic communication skills (e.g., "dials telephone numbers" or "writes messages") in his or her own environment. A total of 43 items assess the rater's observations of a patient's functional status across four domains (Social Communication; Communication of Basic Needs; Reading, Writing, and Number Concepts; and Daily Planning). A 7-point ordinal scale is used to rate the patient's level of independence....

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